Save to Disk is perfect for sharing a book.
Pick a format for their reader first or you may get lots of extra files depending on your library.
Save to anywhere (including USB)
Definately NOT for backup

So can you explain Calibre library more to me please then
I musn't mess inside it then
1. So if I want to give a friend one of my drm feee epubs do I take the whole library to them on a memory stick? - if I dont go inside the Calibre folder .Then what.

2. Also if my Kobo keeps slowing down (as it is doing) if I then reset it(is this a good idea also?) -- How do I re add my books through Calibre again?

3. Plus if I want to stop using Calibre for some reason what happens to my books?
How do I add them then?

Save to Disk is perfect for sharing a book.
Pick a format for their reader first or you may get lots of extra files depending on your library.
Save to anywhere (including USB)
Definately NOT for backup

But how do I save to disc? Why not for back up is it not the same thing? Well confused here lol

So can you explain Calibre library more to me please then
I musn't mess inside it then
1. So if I want to give a friend one of my drm feee epubs do I take the whole library to them on a memory stick? - if I dont go inside the Calibre folder .Then what.

2. Also if my Kobo keeps slowing down (as it is doing) if I then reset it(is this a good idea also?) -- How do I re add my books through Calibre again?

3. Plus if I want to stop using Calibre for some reason what happens to my books?
How do I add them then?

1: That is a great use for STD, send to an external (to the Library) file: drive, device, email temp folder.

3: Deleting Calibre leaves the Library intact. If you have peeked you notice Author folders with title inside those... Your books, just no friendly librarian to find and deliver them.

When you save to disk the book is stored in a folder by author's name. Within that folder is a folder for the book. Within that folder is the book by file type(s), OPF file and I think the book cover file.
You can easily send the folder of the book containing the above to yourself, a usb storage device, cd, etc. or another person via email as attachments.

It is quite easy to do. The options for sending to device are failry wide and easy to use. If you're not sure how it's going to work practice by creating a folder on your computer and send the book to it using Calibre and the varied send to device options.
You could also go through the more laborious method for copy/paste the file/folder from the Calibre library found in explorer but the send to device method via Calibre is much easier.

2. Also if my Kobo keeps slowing down (as it is doing) if I then reset it(is this a good idea also?) -- How do I re add my books through Calibre again?

(Dont know if just deleting all the boks on it and re adding will make it faster again_

But if not and I reset it - I have all my books in Calibre but only 100 of the same ones in ADE . Wont the Kobo need ADE to set it up again and I end up with 100 of my books duplicated?
Sorry all the confusion
Can you just lead me through resetting and re adding books to Kobo
Grateful of all the help here

2. Also if my Kobo keeps slowing down (as it is doing) if I then reset it(is this a good idea also?) -- How do I re add my books through Calibre again?

(Dont know if just deleting all the boks on it and re adding will make it faster again_

But if not and I reset it - I have all my books in Calibre but only 100 of the same ones in ADE . Wont the Kobo need ADE to set it up again and I end up with 100 of my books duplicated?
Sorry all the confusion
Can you just lead me through resetting and re adding books to Kobo
Grateful of all the help here